A bit patterned media (BPM) is expected to extend the data storage density in hard drive disks and anticipated to be the next generation of data storage media. Conventionally, a data storage media 100 may comprise, among others, a base layer 102, a data storage layer 122, and a protective layer 132, as shown in FIG. 1f. Within the data storage layer 122, there may be a plurality of active regions 122a, each of which is used for storing a single data bit, and one or more separators 122b for isolating each active region 122a. In the conventional BPM 100, the active regions 122a are formed when BPM 100 is manufactured. This is contrary to earlier data storage media, where the active regions are formed while the data is recorded. As the storage capacity of a media depends on the number of the active regions 122a, a BPM 100 with greater number of active regions 122a is preferred.
In manufacturing the conventional BPM 100, the data storage layer 122 is formed above the base layer 102 and an intermediate layer 122 (FIG. 1a). The material in the data storage layer 104 may be magnetic material containing species that exhibit ferromagnetism. Thereafter, a resist layer 108 is deposited on the data storage layer 122 and patterned using a known lithographic process as shown in FIG. 1b. Examples of the known patterning process may include photolithographic process, nano-imprint lithographic process, and direct write electron beam lithographic process. As a result, a portion of the data storage layer 122 is exposed.
The exposed portion of the data storage layer 122 is then etched using, for example, an ion milling process. In this process, reactive ions 132 are directed toward the exposed portion of the data storage layer 122, and the material therein is removed (FIG. 1c). Meanwhile, a portion of the data storage layer 122 shielded from the reactive ions 152 by the resist 108 may remain on the base layer. If viewed from the side, the resulting media 100 may comprise columns 122a of ferromagnetic material spaced apart and isolated from each other by gaps. Such columns 122a may ultimately form the active regions 122a. Areas between the columns (e.g. gaps) are then filled with non-magnetic material with low permeability and remanence. This non-magnetic material forms the separators 122b (FIG. 1d). Thereafter, the media 100 is planarized (FIG. 1e), and a protective coating 152 is deposited on the data storage layer 122 (FIG. 1f). The resulting BPM 100, as noted above, comprises a data storage layer 122 having a plurality of active regions 122a isolated by one or more non-magnetic separators 122b. 
As an improvement, a process of manufacturing BPM that incorporates ion implantation step has been proposed. This process is shown in FIG. 2a-2e. It should be appreciated by those of ordinary skill in the art that many components in FIG. 1a-1f are also incorporated into FIG. 2a-2e. As such, many of the components in FIG. 2a-2e should be understood in relation to FIG. 1a-1f. 
First, the data storage layer 122 is formed on the base layer 102. Thereafter, the resist layer 108 is deposited on the data storage layer 122 (FIG. 2a). The resist layer 108 is then patterned using one of the known lithographic processes, and at least one region of the data storage layer 122 is exposed (FIG. 2b). When viewed from the top, the exposed region of the data storage layer 122 is surrounded by the non-exposed portion of the data storage layer. Thereafter, ions 234 are introduced and implanted into the exposed region of the data storage layer 222 (FIG. 2c). The ions 234, when implanted, convert the material in the exposed region from ferromagnetic material to a non-magnetic material with low permeability and ideally no remanence. This non-magnetic material may be the separator 222b. Meanwhile, material in the region 222a shielded from the ions 234 by the resist 108 may remain ferromagnetic and form the active regions 222a of the BPM 200 (FIG. 2d). The active region 222a may be surrounded and isolated from neighboring active region 222a by the separators 222b. After the active region 222a and the separator 222b are formed, the remaining resist 108 is removed, and the protective layer 152 is deposited thereon (FIG. 2e).
In this process, the separators 222b may form via various mechanisms. In one approaches, the separator 222b is formed via dilution of magnetic material. In this approach, the ferromagnetic material in the exposed region of the data storage layer 222 is implanted with species that do not exhibit magnetic property. With sufficient dose, Curie temperature of the resulting material is reduced to room temperature such that the material is no longer magnetic at room temperature. To achieve sufficient dilution, atomic concentration of ˜10% or more of the diluting ions may be needed. For a media comprising cobalt (Co) based data storage layer of 30 nm thickness, a 10% concentration implies an ion dose of approximately 3×1016/cm2. This dose may be proportional to the thickness of the storage layer and thus may be less if the data storage layer is thinner.
In another approach, the magnetic material in the exposed region of the data storage layer 122 may be converted into nonmagnetic material via alteration of the material's crystallinity or microstructure. The ion implantation process is an energetic process that can cause many atomic collisions. During implantation, the material in the exposed region that is otherwise crystalline may become amorphous and/or disordered. As a result, the material may exhibit low ferromagnetism at room temperature. Meanwhile, the material shielded by the resist 108 may retain its original magnetic property. This approach may be effective if the original ferromagnetic layer is a multilayer that derives its magnetic properties from the interaction of very thin layers in a stack. However, this approach may also require a high ion dose. A typical ion dose necessary to amorphize/disorder a silicon substrate is 1×1015 ions/cm2 or higher. In a metal substrate, this required dose may be even higher, particularly if the implant is performed at room temperature.
Both approaches, however, have several drawbacks. One such drawback may be limited throughput caused in part by the high ion dose requirement. As noted above, each approach in forming the separator 222b requires an ion dose ranging about 1×1016-1×1017 ions/cm2. However, the beam current in a conventional ion implanter is limited due to the limitations in generating the ions. Accordingly, such a high dose will limit the throughput or increase the time the ion implantation system has to process the media. With limited throughput, the cost associated with manufacturing BPM may be high.
The throughput may also be limited in part by the resist patterning step. As noted above, the electron beam direct write patterning step may be used to pattern the resist. In this process, an electron beam is scanned along one or more directions to directly write or pattern the resist. Although this process enables greater resolution, this process is very slow and it is not suitable for high throughput production.
The nano-imprint lithography process, a more efficient resist patterning, may be incapable of producing resist with desired properties. For example, the maximum practical resist height achieved in the nano-imprint lithography process may be limited to about 50 nm. Such resist may not survive the subsequent high dose ion implantation process and/or adequately protect the material underneath. A portion of the resist may sputter away during ion implantation, and portions of material outside of the exposed region (i.e. material originally under the resist 108) may be implanted with ions and also converted into the separator 222b. Accordingly, less than optimal BPM may result.
Moreover, high dose ion implantation used to form the separator 204a may also contribute to sputtering of the material in the exposed region. This sputtering effect proceeds in proportion to the total dose needed to form the separator 222b. This sputtering effect may result in a non-planar storage layer. Because the BPM manufacturing process that incorporates the ion implantation step is intended to omit the gap filling step (e.g. FIG. 1d), excessive non-planarity between the exposed region and the unexposed region may be highly undesirable.
Accordingly, a new method for manufacturing hit pattern media is needed.